U.S. Sen. Brian Schatz of Hawaii speaks at a news conference in Honolulu in August.

Audrey McAvoyAP

It says something about the changing politics of Hawaii that Democratic powerhouse Daniel Inouye's deathbed pick of a successor was ignored by his own party.

The question is what.

The December 2012 death of the long-serving senator — and one of the state's founding fathers — has exposed cracks in Hawaii's solidly Democratic façade, leading to a contentious Senate primary that has placed age, gender and ethnicity at center stage.

The combatants are two respected liberals: Sen. Brian Schatz, a white, 41-year-old former lieutenant governor appointed to serve out Inouye's unexpired term; and U.S. Rep. Colleen Hanabusa, 62, the senator's bypassed Japanese-American protégé.

The too-close-to-call primary contest won't affect control of the Senate — the winner of the Aug. 9 primary is expected to easily retain the seat Inouye held for five decades.

But it will reveal much about Hawaii's new political order, which is slowly being remade by demographic and generational forces.

Just How Different?

Despite their supporters' snarling — as well as the money and involvement of competing national liberal groups — Hanabusa and Schatz have fairly similar legislative records.

"Ideologically, I really don't think you could slip a dime between them," says Jerry Burris, a former political columnist at The Honolulu Advertiser. "Both are liberals, both are progressives.

"If there is a divide between them," he says, "it's the old-style politics versus the new-style politics."

But there are fine ideological distinctions that progressive activists have seized on — such as Hanabusa's membership in the New Democrat Coalition (a centrist-oriented, business-friendly group) and the congresswoman's slow embrace of gay marriage.

While Hanabusa has the blessing of Inouye's widow and support from EMILY's List, a group that supports Democratic female candidates who support abortion rights, Schatz has corralled the backing of the national party, as well as prominent environmental and union organizations.

Schatz was an early Obama supporter during his first presidential run in 2008; Hanabusa joined her mentor, Inouye, in support of Hillary Clinton in that race. Obama, who was born in Hawaii, defeated Clinton in the state caucuses with 76 percent of the vote.

The recent involvement of the Progressive Change Campaign Committee, a liberal activist group, has upped the rhetoric.

"I see this race as a proxy between the Elizabeth Warren wing of the Democratic Party and the corporate wing of the Democratic Party," says Adam Green, a PCCC co-founder and former MoveOn online organizer.

Green spoke from Hawaii, where the PCCC last week began training volunteers to work on behalf of Schatz.

His group is attempting to use the issue of Social Security to distinguish between the candidates. Schatz has endorsed an expansion of the entitlement program favored by progressive Democrats; PCCC asserts that Hanabusa has "refused to rule out cutting benefits."

The congresswoman, in a statement this week, said that she has "always fought changes to Social Security that would reduce benefits, and I am particularly opposed to cuts that are designed to balance the budget."

Hanabusa and her supporters have been trying to get political mileage out of Gov. Neil Abercrombie's comment that one reason he appointed Schatz to the seat was because he was younger and had a better chance to build seniority in the Senate — an important issue in a state that's dependent on federal spending and geographically distant from the mainland.

Hanabusa described that logic as "rather offensive," and her supporters see the argument as a slight to women.

"To try and disqualify someone as experienced and as committed as Colleen Hanabusa just doesn't make sense," says Marcy Stech of EMILY's List. "Women in Hawaii are paying attention."

The blessing of the progressive wing of the state Democratic Party goes a long way, says Dylan Nonaka, the former executive director of the Hawaii GOP.

"My simple take on that is there's been a clear trend in Hawaii that in Democratic primaries, the thing that trumps all — age, gender, ethnicity — is ideology," says Nonaka. "I think Brian Schatz has picked up on that and is defining himself as the candidate more to the left."

In typically low turnout primaries, he notes, liberal activist groups will have huge sway in the outcome.

Changing Demography

The state's changing electorate could also play a role in determining the outcome of the primary. While Japanese-Americans once had a firm grip on state politics, that population has been declining fairly rapidly over time, says Mark Mather, a demographer with the Population Reference Bureau. In the 2010 census, Filipinos became the state's largest single ethnic group.

"Around 1960, when Dan Inouye was starting his Senate career, about a third of Hawaiians were Japanese-Americans," he said. "Now it's 14 percent."

The white population, meanwhile, has held steady at about a quarter of the population — Nonaka points to the political influence of wealthy white retirees from the mainland.

But the fastest growing demographic, Mather says, is among residents who identify as multiracial.

"Hawaii is sort of the ultimate melting pot," he says. "About a fourth of the population identify with two races." And about 8 percent identify with three or more races — double the percentage in California.

In any case, Burris cautions against drawing political conclusions based on demographic changes.

"People tend to look at Hawaii and tend to see ethnic politics as critical, but I think that analysis can be overplayed," he says.

His prediction?

"The only one I can make is that there are three parties — Republicans, Democrats and incumbents. I always tend to think incumbents, even short-term incumbents, have the advantage."